...and for the record and with all due respect, going to the trouble of producing a video driver for the OS, but dropping OpenCL support for it seems like a silly silly decision.
TO put it another way, they produced a driver for the "closed" "proprietary" windows OS, and dropped support for the "open" software.

Dropping support for an ancient OS is normal. The drivers that they make need to be able to run on the older OS, and preferably without too many problems.

There's no support for Windows 95/98/ME/SE either, I don't see you complain about those. XP will just join that list, and rightly so. It's getting too old now to be of any use with newer hardware as it's becoming more and more difficult to add complete support for new hardware into the old OS. Jord

Ancient Astronaut Theorists suggest that in many ways, you can be considered an alien conspiracy!

Our definitions of ancient might differ, and since AMD produced a driver for the 7770 for XP they seem to see agree with me that as old as XP is, it's not completely put out to pasture just yet.

AMD made a video driver for it, and they'll probably continue doing so until April 8, 2014 or thereabouts.

It's the OpenCL component of the driver that they didn't add, most probably because of things that OpenCL can do on newer OSes --fully supported programmable options-- that the older OSes no longer can do, or only (badly) with lots of programming around it (called bloating).

You can compare it to running Windows XP on a 64bit CPU. The register acronyms that the CPU has will lack features when seen through Windows XP, when compared to seen through Windows 7, just because Windows 7 has full support for these and is programmed to recognize them.

With new standards like OpenCL adding significant functionality with each specification release, it's getting worse for driver writers to support the older OSes as these just don't support the handles that the new specifications add. At such a point it's easier to just stop supporting the OS, than to try to write code around it that will make OpenCL work on the older OS, but probably break other things in the driver.

On the box, Windows XP is listed as supported without an asterisk of any kind.

Which is correct for what a video card is intended for: translating the electronic output into visual input shown on a monitor or TV.

Video cards/Graphics cards are still sold for just that: outputting to a monitor. They're not yet sold solely with GPGPU in mind. The general public doesn't need to know about that yet.Jord

Ancient Astronaut Theorists suggest that in many ways, you can be considered an alien conspiracy!